The only problem is that it's only playable in Firefox and you cannot load a ROM from your computer. You have to (temporarily) host it on Dropbox or another cloud file storage service, then provide the URL to the emulator. It's also in beta and some games will most likely look very weird or glitched. But it's still worth a try since it gives a new experience from playing your favorite classics. I wonder if most 3D stuff like pipes are hard-coded or detected automatically...

If you try it, you should post screenshots of what your favorite games look like

If you mean how some graphics sometimes pops out or in, then that's most likely glitchyness. You can change the render quality in the settings, though. But if you mean the camera angle, then yes you can change it at will.

On a side note, anybody knows how to generate the dl.dropboxusercontent.com/u/ version of a Dropbox URL? Because I think the emulator only works with that version, not the www.dropbox.com/gibberisheiwiwide format, and when I go to my Dropbox profile, the Share option only gives me the latter URL format.

Also the emulator has issues handling slopes (eg in World 1-2 of Super Mario 3). I really wonder how well it handles parallax scrolling in Battletoads.

I think it needs some perfecting, though. Of course it would be impossible to do it without presets for each game, though, but I think some stuff like the backgrounds/foregrounds randomly changing positions could be fixed. Nonetheless this is still cool and Contra looks amazing.